Coatings are typically applied to the interior of metal food and beverage containers to prevent the contents from contacting the metal surface of the container. Contact with certain foods, particularly acidic products, can cause the metal container to corrode. This corrosion results in contamination and deterioration in the appearance and taste of the food or beverage product.
Corrosion problems are particularly acute with soups containing high levels of KCl such as chicken rice soup. Although coating compositions such as those based on polyglycidyl esters of bisphenol A can provide excellent corrosion protection for acidic food stuffs, coatings made with bisphenol A and derivatives thereof are problematic. These materials are perceived as being harmful to human health. Consequently there is a strong desire to eliminate these materials from coatings in contact with food stuffs.
Coatings based on oleoresinous materials such as organic oils are also known to provide excellent corrosion resistance; however, these coating compositions are organic solvent based and have high levels of volatile organic compounds (VOCs) that are also harmful to human health. It would be desirable to use aqueous-based coating compositions that have lower VOCs.